Peter,
great choice with the Nikon D50, to be honest at this level of equipment the most important thing is the feel of it in your hands and how good it feels to the eye, as for the difference between the Nikon and the Canon......well, thare aint much in it to be honest, however you were advised correctly on the quality of the kit lens with the Nikon, not to say you cant buy good lenses with the Canon, but they tend not to bundle it in the kit with the 350,
as you have said already , the secret is to take lots and lots of pix, for one it doesnt cost you anything to do so, and the second is the more you take the better you will get , make sure you pop a few up on here for some friendly critique , and general pointers ( if you need any )
happy snapping
MyPix